An internal combustion engine, as well as other devices, produce unwanted acoustic waves or noise. The combustion of air and fuel creates noise. The operation of pistons, crankshafts, gears, belts and pulleys creates noise. A muffler, which may also be referred to as a silencer, provides structure for reducing the noise or magnitude of the acoustic waves. The muffler may include materials that partially absorb the acoustic waves. The muffler may include structure that introduces destructive interference to reduce the magnitude of the acoustic waves. Challenges remain in maximizing the reduction in noise or magnitude of acoustic waves produced by the internal combustion engine.